(600bv) The Relationship Between Enhanced Enzyme Activity and Structural Dynamics in Ionic Liquids: A Combined Computational and Experimental Study

Candida antarctica lipase B (CALB) is an efficient biocatalyst for esterification, and polymerization reactions. In order to understand how to control an enzyme activity and stability we performed a combined experimental and molecular dynamics simulation study of CALB in organic solvents and ionic liquids. Our results demonstrate that the conformational changes of the active site cavity are directly related to enzyme activity. We indicates that CALB activity in synthetic solvents decreases with an observed solvent-induced reduction in the size of the substrate binding cavity in the following order: [Bmim][TfO] > tert-butanol > [Bmim][Cl]. The size of the active site cavity is modulated by an α-10 helix, which can substantially change its conformation due to specific interactions with solvent molecules. This change is evident in [Bmim][Cl] where interactions of LYS-290 with chlorine anions induced a conformational switch from an α-helix to a turn, which resulted in reduced activity. Moreover, the relation between the enzyme-solvent interfacial energies and initial reaction rates show a linear trend; these results predict that the initial reaction rates increased with a reduction in interfacial energy. Overall, our observations can be used to explain the structure-activity relation of CALB in various solvents, as may be applicable for the selection of appropriate solvents in order to optimize enzymatic reactions.